1. Field of the Invention
The invention relates to voice messaging systems for use in telecommunication networks, particularly with respect to parameter transfer protocols between call intercept units and a message delivery system thereof.
2. Description of the Prior Art
Voice messaging systems are known where a call is intercepted upon detection of an incomplete call condition at the intended call destination. The system issues a prompt to the caller offering a voice store and forward service for caller acceptance. The incomplete call condition may, for example, be a busy or ring-no-answer (RNA) condition at the called telephone. Such systems normally include one or more Intercept Processing Units (IPU) and a Message Delivery System (MDS). The MDS is often referred to as a Voice Processing Subsystem (VPS). The IPU may be installed in the subscriber loops connecting the user telephones to the telephone company (telco) Central Office (CO), or the IPU may be installed in the digital links interconnecting the telco network switches. Alternatively, the IPU may be located at the telephone or functionality of the IPU may be incorporated in the telco switch. The MDS is normally connected by a trunk to either a telco switch or to the IPUs or both, depending on the configuration, and is accessible by either a dialed or dedicated connection. Systems of this type are described, for example, in U.S. Pat. Nos. 5,34,646; 5,036,533; 4,932,042; 4,901,341 and 4,766,604. Pending U.S. patent application Ser. No. 08/016,588, filed Feb. 10, 1993, also discloses such a system.
Call intercept/message delivery systems of the type described are particularly advantageous in pay telephone networks and are denoted as Coin Voice Messaging Systems (CVMS). In a CVMS system, the IPUs intercept calls from paystations and either route them to the normal telephone company network, or in the case of a busy signal or RNA at the distant phone, offer through voice prompts the service to store and forward a message. The prompts instruct the payphone customer to deposit coins to accept the service or to enter a designated key sequence if the call had been charged to accept the service. Acceptance of the service through coin insertion is referred to as "sent-paid" and entry of a calling card or charge card number is referred to as "non-sent-paid".
The IPU subsystem is commercially available from, for example, Cordell Manufacturing Inc. of Covina, Calif., as the Advanced Paystation Interface System (APIS) or from Science Dynamics Corporation of Cherry Hill, N.J., as the Coin Line Monitor Interceptor (CLMI). The MDS subsystem is a commercially procurable system available from numerous sources. For example, Unisys Corporation of Blue Bell, Pa., provides a unit denoted as the Unisys Voice Processing Subsystem (VPS). The VPS is available from Unisys Corporation in a personal computer (PC) version denoted as PC/Vips supported by a UNIX system host processor (UNIX is a trademark of AT&T). Unisys Corporation also provides a Network Applications Platform (NAP) to support the VPS functions with an appropriate resident application. Such an application is available from Unisys Corporation and is denoted as the Coin Voice Messaging System (CVMS). The NAP is described in U.S. Pat. No. 5,133,004, issued Jul. 21, 1992.
In the call intercept/message delivery system, the IPU intercepts the call on busy/ring-no-answer and the caller is offered the opportunity to record a message via the MDS. If the caller accepts the service, the IPU contacts the MDS and communicates call specific parameters such as called telephone number, calling telephone number, credit card numbers and the like over the connection usually utilizing DTMF digits and in accordance with a handshake protocol that is unique to each type of IPU. For example, different types of IPUs may be designed to deliver different strings of parameters in different orders utilizing different field formats. Additionally, the different types of IPUs may be designed to interchange protocol specific acknowledgments with the MDS during parameter transmission. Thus it is appreciated that the handshake protocols between different types of IPUs and the MDS may be different with respect to each other. After the handshake is successfully accomplished, the MDS prompts the caller for the message and then attempts to deliver the recorded message to the original called number.
The systems described have a number of disadvantages. The software of the MDS must be designed to support the particular parameter transfer protocol of the type of IPU in use at the time. Prior art systems generally operate with a single type of IPU at one time and would require software changes to accommodate different types of IPU. It is necessary to change the MDS program to accommodate different IPU types.
Older IPU designs do not collect and transmit a large number of digits to the MDS during the handshake. The IPU-to-MDS transmission can be completed in approximately two seconds. This delay prior to the MDS offering spoken instructions to the caller does not adversely affect the user acceptance of the service. Present day IPUs, however, can collect and transmit significantly more data than the previous designs. When an IPU transmits a large number of digits, the delay experienced by the caller before the caller can record the message would seriously affect user acceptance of the service. This delay is exacerbated since the MDS provides data validation and acknowledgment/negative acknowledgment of each interaction. The delay experienced by the caller after accepting the service offered by the IPU but before hearing the first instructions spoken by the MDS would be unacceptable in conventional user situations.
Systems of the type described tend to be expensive because of the requirement for programming modifications to accommodate different types of IPUs. Since present systems cannot concurrently interact with multiple IPU types, redundancy in resources, such as CPU and memory, is required to support multiple IPU types on a single computer. Such redundancy further increases the cost of the system.